In gas turbine engines a diffuser case for the combustor is normally made of a high nickel super alloy. The fuel injector must be bolted to this diffuser. The diffuser material however, is very hard and difficult to machine. Tapping of holes therein will frequently lead to breakage of the tap and the requirement to electro-discharge machine the tap out of the case or otherwise introduce difficult and expensive repairs.
It is accordingly known to use inserts located in drilled holes through the case. This not only avoids the necessity of tapping these holes, but also avoid the stress concentrations caused by such threading.
The possibility of bolts becoming loose and thereafter ingested into the turbine must be avoided. With non-locking inserts it is required that the bolts be safety wired into place. The nature of this wiring is critical and very time consuming. Furthermore a supply of wire must be maintained at each supply depot.
Various other self locking arrangements have been found to be difficult to install and or remove when required.
A self locking insert arrangement is required which is inexpensive, reliable and easily replaceable.